In recent years, a hybrid vehicle, a fuel cell vehicle, an electric vehicle and the like that run by using a driving force from a motor are attracting attention as one of the measures against environmental issues. On these vehicles, electrical equipment such as an inverter circuit supplying electric power to the motor is mounted. The electrical equipment drives the motor at high voltage, and it is necessary to ensure insulation. As a vehicle having such electrical equipment and motor mounted thereon, Japanese Patent Laying-Open No. 2004-208409, for example, discloses a vehicle on which a vehicle power control device capable of reducing a loss while responding excellently to various operating modes required by various rotating electric machines for running is mounted.
A vehicle having a motor mounted thereon may run in a highland. In particular, the atmospheric pressure is low in the highland, and discharge is likely to occur under such an environment. This characteristic is mentioned by the Paschen's law. The Paschen's law indicates that a discharge inception voltage is determined by a function of the product of the atmospheric pressure and the distance between electrodes. Therefore, in the electrical equipment and the motor, an amount of partial discharge within insulators is increased. As the amount of partial discharge is increased, the insulation performance of the insulators is degraded. Furthermore, the durability life is shortened.
Since a change in atmospheric pressure is not taken into consideration in the vehicle power control device disclosed in the above publication, the problems described above may arise.